1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a circuit and method of driving a liquid crystal display.
2. Discussion of the Related Art
Generally, liquid crystal display (LCD) devices control light transmittance of liquid crystal cells in accordance with an electrical signal, thereby displaying an image. An active matrix LCD device includes switching devices for each liquid crystal cell, thereby sequentially displaying multiple images to generate a moving image. The active matrix LCD device uses thin film transistors (TFTs) as the switching devices. Since the LCD device has smaller dimensions than a conventional display tube, LCD devices have been widely used in personal computers, notebook computers, office automation equipment such as copy machines, for example, and portable equipment such as cellular phones and pagers, for example.
Presently, polycrystalline silicon panels are used for switching devices and devices for peripheral driving circuits of the active matrix LCD. A polycrystalline silicon driving circuit sequentially applies data voltage from a first data line to a last data line while a gate line is held in an ON-state, thereby decreasing writing time. However, as polycrystalline silicon panels become bigger, the data and gate lines become longer, parasitic capacitance and resistance increase, and the display signal is delayed. Accordingly, to drive the polycrystalline silicon panel, a block driving method is used that divides the data line into several blocks.
FIG. 1 shows a circuit diagram of a display panel driven by a block driving method according to the conventional art.
In FIG. 1, data switches φ1, φ2, . . . φn sequentially connect data signals transmitted via signal lines Si−1, Si, Si+1 to data lines DL1, DL2, . . . DLn, and pixel switches P1, P2, . . . Pn transmit the data signals to corresponding pixels (not shown). For example, a data signal is input through the signal line Si, and upon enabling the data switch N1, the pixel switch P1 is turned ON through a first data line DL1 to apply the data signal to a corresponding pixel (not shown). Almost simultaneously, the data switch φ2 is turned ON, and the data signal Si is transmitted to a second pixel (not shown) through a second data line DL2 and a second pixel switch P2. This switching operation is continuously repeated until the data switch φn is turned ON.
FIG. 2 shows a driving waveform of the block driving method shown in FIG. 1.
In FIG. 2, when transmitting a data signal to a gate line GL, a gate input signal GI is applied to close the pixel switch. Then, the data signal is sequentially applied to first through nth data lines DL1 to DLn Accordingly, a delay is generated between a time t1 when a data signal Si is transmitted by the first data switch φ1 to the first pixel and a time tn when the data signal Si is transmitted by the nth data switch φn to the nth pixel, thereby creating a vertical stripe on the display panel. Furthermore, since liquid crystal capacitance increases at low operating temperatures, the vertical stripe is more prominent.